JP2006000731A - Motor control device and centrifuge using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device capable of suppressing the generation of heat in a motor to suppress a rise in the temperature of the ball bearing of a motor bearing part, and a centrifuge using the same. <P>SOLUTION: The centrifuge 200 has a rotor 1 for housing a sample, a motor 2 for rotationally driving the rotor 1, a speed detecting sensor 3 for detecting the present rotational speed of the motor 2, an inverter 4 for driving the motor 2, a control part 5 for controlling the inverter 4 and a motor current detector 10 for detecting the current of the motor 2. A voltage modulated wave forming part 6, a carrier forming part 7, a PWM (pulse width modulation) signal forming part 8 for comparing the magnitude of a voltage modulated wave with that of a carrier to output a PWM signal to the inverter 4 and a carrier frequency indicating part 9 for outputting a carrier frequency to the carrier forming part 7 are installed in the control part 5. The carrier frequency indicating part 9 determines the carrier frequency at the time of setting so as to make the same higher than that at the time of acceleration and deceleration in the acceleration and deceleration operation or setting operation of the motor to suppress the generation of heat in the motor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device that controls the rotational speed of a motor that drives a centrifuge rotor and the like, and a centrifuge using the control device.

  2. Description of the Related Art As a control device for a centrifuge motor, a control device including a power factor improving converter and an inverter is known. In the power conversion between the AC source and the DC source, the power factor improving converter functions as a step-up converter for conversion from the AC source to the DC source, functions as a step-down converter for conversion from the DC source to the AC source, and Suppresses harmonic components of current flowing from AC power supply. In the power conversion between the direct current source and the motor, the inverter controls the motor that rotationally drives the rotor using the direct current source as the electric power source to perform power running and regenerative operation.

This control device uses a DC power source boosted by the power factor correction converter to drive a motor applied voltage through an inverter during acceleration to increase the rotor rotation speed by powering the motor or during settling to keep the rotor rotation speed constant. The motor is driven by PWM voltage control for controlling the above and positive slip control. When decelerating to reduce the rotational speed of the rotor by regenerating the motor, the motor is driven by the PWM voltage control and negative slip control via the inverter, and the electric energy regenerated by the DC power source is converted to a power factor improving converter. The voltage is stepped down and returned to the AC power supply (see, for example, Patent Document 1).
JP-A-7-246351 (page 9, FIG. 2)

  In the conventional motor control device described above, the DC power supply voltage is maintained at a voltage higher than the peak value of the AC power supply voltage by the power factor improving converter that converts the AC power supply to the DC power supply during acceleration / deceleration of the motor. Since the motor applied voltage is controlled by adjusting the modulation factor of the PWM voltage control, the control of the voltage applied to the motor is insufficient.

  In addition, in an ultracentrifuge that controls the vacuum inside the chamber that houses the rotor and rotates the rotor at a high speed, the windage loss of the rotor can be ignored, so the motor load during settling is 1/10 of the motor load during acceleration. To a degree. For this reason, the control device described above needs to reduce the motor applied voltage so as to reduce the motor input power, and the modulation rate of the PWM voltage is reduced. However, at this time, the harmonic component of the motor current is increased, the reactive power is increased, the heat generation of the motor is increased, and the temperature of the ball bearing at the motor bearing is increased.

  The present invention has been made in view of the above-mentioned problems, and its purpose is to reduce the harmonic component of the motor current, suppress the heat generation of the motor, and suppress the temperature rise of the ball bearing of the motor bearing portion. It is an object to provide a motor control device and a centrifuge using the control device.

The invention according to claim 1, which has been made to solve the above problem, includes a speed detection sensor that detects a current rotation speed of a motor, a drive unit that drives the motor, and a control unit that controls the drive unit. The control unit includes: a voltage modulation wave generation unit that generates a voltage modulation wave that is a target of a phase voltage applied to the motor; a carrier generation unit that generates a carrier; and a magnitude of the voltage modulation wave and the carrier. A drive signal generation unit that outputs a drive signal generated by the comparison to the drive unit, a carrier frequency of the carrier is determined according to an operation state of the motor detected by the speed detection sensor, and the carrier generation unit A carrier frequency indicator for outputting the carrier frequency;
The carrier frequency indicating unit is a motor control device characterized in that the carrier frequency at the time of settling of the motor is made higher than the carrier frequency at the time of acceleration / deceleration.

  In the control device according to claim 1, the speed detection sensor detects the rotation speed of the motor and outputs it to the control unit. The carrier frequency instructing unit of the control unit instructs the carrier generating unit to use a higher carrier frequency than during acceleration / deceleration when the detected motor operating state is settling. The drive signal generation unit generates a drive signal using the carrier output from the carrier generation unit and the voltage modulation wave.

  According to a second aspect of the present invention, in the control device, the control unit includes an asynchronous mode in which the carrier frequency is constant regardless of a change in the frequency of the voltage modulation wave, and a change in the frequency of the voltage modulation wave. The carrier frequency further has a mode switching means for switching between a synchronous mode in which the phase of the voltage modulated wave and the carrier is always synchronized with the frequency of the voltage modulated wave, and the mode switching means includes: At the time of acceleration / deceleration of the motor, when the frequency of the voltage modulation wave is below a predetermined value, the mode is switched to the asynchronous mode, and when the frequency of the voltage modulation wave exceeds a predetermined value, the mode is switched to the synchronous mode. It is characterized by switching to the synchronous mode at the time of settling.

  According to a third aspect of the present invention, the control device further includes a motor current detector that detects a current of the motor, and the control unit is configured to detect a current of the motor by the motor current detector during a settling operation of the motor. The carrier frequency is adjusted according to the size of the signal.

  The invention according to claim 4 includes a motor, a rotor connected to the motor for rotation, and the motor control device according to claim 1 for controlling the rotation of the motor. Machine.

  According to the control device of the first aspect, the carrier frequency indicating unit makes the carrier frequency at the time of set higher than the carrier frequency at the time of acceleration / deceleration during the acceleration / deceleration or settling operation of the motor. This can reduce the heat generation of the motor and suppress the temperature increase of the ball bearing of the motor bearing.

  According to the control device of the second aspect, at the time of acceleration / deceleration, the synchronous mode and the asynchronous mode can be switched according to the motor excitation frequency, and the carrier frequency does not need to be changed at a low rotation, and the control becomes easy. Since the synchronous mode is used at the time of acceleration / deceleration at a predetermined rotational speed or more and during settling, voltage fluctuation can be suppressed.

  According to the control device of the third aspect, since the carrier frequency during settling is set according to the motor current amount, it is possible to suppress the heat generation of the motor.

  According to the centrifuge of the fourth aspect, since the motor that rotates the rotor is prevented from generating heat and the temperature increase of the ball bearing of the motor bearing portion is suppressed, the temperature increase inside the centrifuge can be suppressed.

  Hereinafter, a control device for a centrifuge motor according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing a configuration of a centrifuge 200 provided with a control device 100 according to the present embodiment, and FIG. 2 shows a configuration of the centrifuge 200 provided with the control device 100 according to the present embodiment. It is a block diagram.

  As shown in FIG. 1, the centrifuge 200 includes a main body 30 and a door 33. An opening 31 is formed in the upper portion of the main body 30. The door 33 is provided in the upper part of the main body 30 and can open and close the opening 31. A keyboard 35 and a display unit 36 are provided in the upper part. The user can input necessary information such as the name of the sample to be centrifuged, for example, from the keyboard 35 while viewing the display unit 36, and can confirm the value input on the display unit 36.

  Inside the main body 30, a rotor 1, a motor 2, a control device 100, and the like are provided. The rotor 1 is used for storing a sample and centrifuging it. The motor 2 is configured by an induction motor or the like. The rotor 1 is connected to the motor 2 via the drive shaft 37, and rotates when the rotational drive torque is transmitted from the motor 2 to the rotor 1 via the drive shaft 37. Therefore, the rotational speed of the motor 2 has a one-to-one correspondence with the rotational speed of the rotor 1. The motor 2 is connected to the control device 100 of the centrifuge 200 for controlling the motor 2. Hereinafter, a detailed configuration and function will be described.

  As shown in FIG. 2, the rotor 1 accommodates a sample and is rotatably provided. The motor 2 is a three-phase induction motor that rotationally drives the rotor 1. The control device 100 includes a speed detection sensor 3, an inverter 4, an inverter control unit 5, a motor current detector 10, and the like.

  The speed detection sensor 3 is a speed detection sensor that detects the current rotation speed of the motor 2. The inverter 4 is a drive unit that outputs a variable frequency voltage to the motor 2. The inverter 4 includes six switching elements 4U, 4V, 4W, 4X, 4Y, and 4Z such as IGBTs and FETs.

  The inverter control unit 5 is a control unit that outputs an on / off signal to the six switching elements 4U, 4V, 4W, 4X, 4Y, and 4Z of the inverter 4. In the present embodiment, for example, the inverter control unit 5 is configured with a microcomputer having a built-in timer for driving a three-phase motor such as a Hitachi SH7065 microcomputer as a core.

  The motor current detector 10 detects the current of the motor 2. The output of the motor current detector 10 is input to the inverter control unit 5.

  The inverter control unit 5 includes a voltage modulation wave generation unit 6, a carrier generation unit 7, a PWM signal generation unit 8, a carrier frequency instruction unit 9, and the like. The voltage modulation wave generation unit 6 generates voltage modulation waves Vu *, Vv *, and Vw * that are targets of the phase voltage applied to the motor 2. The frequency of the voltage modulation waves Vu *, Vv *, Vw * is the motor excitation frequency f1. The carrier generation unit 7 generates a carrier CR. The PWM signal generation unit 8 is a drive signal generation unit, and outputs to the inverter 4 a PWM signal that is a drive signal generated by comparing the magnitudes of the voltage modulation waves Vu *, Vv *, Vw * and the carrier CR. This PWM signal is an on / off signal for the six switching elements 4U, 4V, 4W, 4X, 4Y, and 4Z of the inverter 4. The carrier frequency instruction unit 9 outputs a carrier frequency command fc * to the carrier generation unit 7.

  Next, the operation of the centrifuge 200 will be described with reference to FIGS. 3 to 9, the same parts as those in FIG. 2 are denoted by the same reference numerals.

  FIG. 3 is a diagram illustrating a method of generating a PWM signal that is a drive signal of the motor 2. In FIG. 3, the horizontal axis represents time, and the vertical axis represents voltage. As described above, the PWM signal is an on / off signal for the six switching elements 4U, 4V, 4W, 4X, 4Y, and 4Z that constitute the inverter 4.

The PWM signals Eun22, Evn23, and Ewn24 are the voltage modulation waves Vu *, Vv *, and Vw * that are the targets of the three-phase phase voltage of the motor 2 that is the output of the voltage modulation wave generator 6, and the output of the carrier generator 7. The carrier CR is generated by comparing the size with the PWM signal generation unit 8. The voltage modulation waves Vu *, Vv *, and Vw * are generated according to the equation (1).

In Equation (1), Vm is the voltage amplitude of the voltage modulation waves Vu *, Vv *, and Vw *, and θvn is the phase of the U-phase voltage modulation wave Vu *. In the asynchronous PWM mode, the phase θvn of the voltage modulation wave Vu * is equal to the phase difference Δθv between the top and bottom peaks of the carrier CR (hereinafter referred to as carrier peak and valley respectively) and the previous voltage modulation wave Vu *. From the phase θvn−1, calculation is performed for each peak and valley of the carrier CR by the equation (2).

  Further, the phase difference Δθv in the case of the synchronous PWM mode is obtained by dividing one period 2π (rad) of the motor excitation frequency f1 by the number of peaks and valleys of the carrier CR.

  The PWM signals Eun22, Evn23, and Ewn24 are drive signals generated by the PWM signal generator 8, and when the voltage modulation waves Vu *, Vv *, and Vw * are larger than the carrier CR, the switching element of the upper arm of the inverter 4 4U, 4V, and 4W are turned on, and at the same time, the lower arm switching elements 4X, 4Y, and 4Z corresponding to the upper and lower sides are turned off. On the other hand, when the voltage modulation waves Vu *, Vv *, and Vw * are smaller than the carrier CR, the upper arm is turned off and the lower arm is turned on.

  Signals eUV25, eVW26, and eWU27 indicate voltage waveforms output between the UV phase, VW phase, and WU phase of the motor 2, respectively. When changing the modulation rate of the PWM signal, the amplitude Vm of the voltage modulation wave Vu *, Vv *, Vw * is changed, and the number of carrier CRs in one cycle of the voltage modulation wave Vu *, Vv *, Vw * is changed. When changing, Δθv may be changed by changing the carrier frequency fc.

  Hereinafter, a method for changing the carrier frequency fc will be described with reference to FIGS. FIG. 4 is a block diagram showing a detailed configuration of the carrier frequency instruction unit 9.

  As shown in FIG. 4, the carrier frequency instruction unit 9 includes a carrier mode instruction unit 50 and a carrier frequency instruction unit 51. The carrier frequency instruction unit 9 is input with a motor excitation frequency f1 and a motor current I.

  The carrier mode instruction unit 50 is a switching unit that instructs the generation mode of the carrier frequency command fc * of the carrier frequency command unit 51 based on the operation state of the acceleration / deceleration or settling operation of the motor 2 and the motor excitation frequency f1. The operating state of the motor 2 is determined by a signal (not shown) input from the speed detection sensor 3 according to the rotation speed of the motor 2.

  The carrier frequency command unit 51 outputs a carrier frequency command fc * to the carrier generation unit 7 according to the operating state of the acceleration / deceleration or settling operation of the motor 2. At the time of acceleration / deceleration of the motor 2, the generation method of the carrier frequency command fc * is switched based on the motor excitation frequency f1, the operation state, and the motor current I based on the motor excitation frequency f1 and the operation state.

  The carrier frequency command unit 51 includes an asynchronous mode carrier frequency command unit 51a and a synchronous mode carrier frequency command unit 51b. The asynchronous mode carrier frequency command unit 51a generates a carrier frequency command fc * corresponding to the carrier frequency fc of the carrier CR to be generated in the asynchronous PWM mode in which the carrier frequency fc is constant regardless of the motor excitation frequency f1. 7 is output. The synchronization mode carrier frequency command unit 51b is a synchronization in which the carrier frequency fc is an integer multiple of the motor excitation frequency f1, and the phase of the voltage modulation waves Vu *, Vv *, Vw * and the phase of the carrier CR are always synchronized. In the PWM mode, a carrier frequency command fc * corresponding to the carrier frequency fc of the carrier CR to be generated is output to the carrier generation unit 7.

  Next, the carrier frequency change at the time of acceleration / deceleration of the motor 2 will be described. FIG. 5 shows a change in the carrier frequency command fc * in the carrier frequency command unit 51 in FIG. 4 in accordance with the change in the motor excitation frequency f1 when the motor 2 is accelerated or decelerated. During acceleration / deceleration, the motor 2 is driven in the asynchronous PWM mode when the motor excitation frequency f1 is equal to or lower than the predetermined frequency f1a, and in the synchronous PWM mode when the predetermined frequency f1a is exceeded.

  In FIG. 5, section I is an asynchronous PWM mode section in the asynchronous mode carrier frequency command section 51a, and sections II to IV are synchronous PWM mode sections in the synchronous mode carrier frequency command section 51b. The frequency f1a is a motor excitation frequency when the asynchronous PWM mode section I is switched to the synchronous PWM mode section II, and the frequencies f1b and f1c are motor excitation frequencies when the number of carriers is switched.

  The frequency fc1 is a constant carrier frequency in the asynchronous PWM mode section I, and the frequency fc2 is an upper limit of the carrier frequency when the motor 2 is accelerated / decelerated.

  In the present embodiment, IBGT is used as the switching element constituting the inverter 4, and for example, the frequency fc1 is 10 kHz, and the upper limit frequency fc2 of the carrier frequency during acceleration / deceleration is 12 kHz. The boundary motor excitation frequency f1a between the asynchronous PWM mode and the synchronous PWM mode is set to 400 Hz so that the number of carriers is 25 or more when the frequency fc1 is fixed at 10 kHz. In addition, the number of carriers in the synchronous PWM mode is 21 in section II, 15 in section III, and 9 in section IV. Motor excitation frequencies f1b and f1c at the time of switching the number of carriers are such that the carrier frequency fc is the frequency fc2. The frequency f1b is set to 571 Hz and the frequency f1c is set to 800 Hz so as not to exceed 12 kHz.

  Next, the operation of changing the count value of the counter clock in the carrier generator 7 when changing the carrier frequency fc will be described with reference to FIG. FIG. 6 is a diagram showing temporal changes in the counter value of the voltage modulation wave Vu * determined by the voltage modulation wave generator 6 and the carrier count value determined by the carrier generator 7 when the carrier frequency is changed. It is. Here, the temporal change of the counter value other than the vicinity of the phase 0 of the voltage modulation wave Vu * is omitted.

  In FIG. 6, carrier CR ′ indicates a temporal change in the count value of the carrier generation unit 7, and the counter of the carrier generation unit 7 counts up from the carrier valley to the carrier peak and decreases from the carrier peak to the carrier valley. Count. For example, the section P shows the relationship between the carrier CR ′ during acceleration / deceleration in the synchronous PWM mode and the U-phase voltage modulation wave Vu *, and the section Q shows the carrier CR ′ and U-phase voltage during settling. The relationship of the modulated wave Vu * is shown. The count value X is the count value of the carrier CR ′ at the time of acceleration / deceleration, and the count value Y is the count value of the carrier CR ′ at the time of settling. Here, the count values X and Y are values calculated by the carrier generation unit 7 based on the carrier frequency command fc * output from the carrier frequency instruction unit 9, and the counter internal clock frequency is doubled. The value divided by fc *.

  When the motor 2 is set, the carrier frequency instruction fc * output from the carrier frequency instruction unit 9 to the carrier generation unit 7 is increased as in the section Q, so that the count value of the carrier generation unit 7 is added like the count value Y. It becomes smaller than the count value X at the time of deceleration, and the carrier frequency fc at the time of settling can be made higher than at the time of acceleration / deceleration.

  In the control device 100 according to the present embodiment, IBGT is used for the switching element of the inverter 4. In general, the switching loss of the IGBT increases and decreases in proportion to the carrier frequency and the current flowing through the motor 2. Here, the rotor 1 in FIG. 2 is kept in a vacuum state by a chamber (not shown) and a vacuum pump. Since the rotor 1 rotates in vacuum, windage loss can be ignored and the output of the motor 2 is reduced.

  When the acceleration / deceleration of the motor 2 is large and the current flowing through the motor 2 is large, the switching element has a large switching loss. Therefore, it is necessary to limit the carrier frequency. The current becomes smaller. Since the switching loss of the switching element increases in proportion to the product of the current flowing through the motor 2 and the carrier frequency, switching of the switching element of the inverter 4 even if the carrier frequency at the time of settling is higher than the carrier frequency at the time of acceleration / deceleration. Loss can be reduced as much as during acceleration.

  In the control device 100 according to the present embodiment, the carrier frequency instruction unit 9 operates so that the carrier frequency command fc * is higher than the command during acceleration / deceleration when the motor 2 is set. As a result, the number of carriers in one cycle of the motor excitation frequency f1 when the motor 2 is set can be increased, so that the harmonic component of the motor current at the settling time can be reduced, and the ball of the motor 2 bearing portion can be reduced. The temperature rise of the bearing can be suppressed.

  Further, in the control device 100 according to the present embodiment, the carrier generation unit 7 sets the voltage modulation waves Vu *, Vv *, and Vw * so that the motor torque is not disturbed when switching from the asynchronous PWM mode to the synchronous PWM mode. The carrier is adjusted so that the phase of the carrier CR coincides with phase 0.

  The state of the count value of the counter in the above adjustment executed by the carrier generation unit 7 will be described with reference to FIG. FIG. 7 shows the count value of the voltage modulation wave Vu * determined by the voltage modulation wave generation unit 6 and the count value of the carrier determined by the carrier generation unit 7 when the PWM mode is changed from the asynchronous mode to the synchronization mode. It is the figure which showed the time change. Similar to FIG. 6, the temporal change of the count value other than the vicinity of the phase 0 of the voltage modulation wave Vu * is omitted.

  In FIG. 7, section R indicates the asynchronous PWM mode, section S indicates the carrier adjustment section, and section T indicates the synchronous PWM mode. The count value X ′ is the count value of the carrier CR ′ in the asynchronous PWM mode and the synchronous PWM mode, and the count value Y ′ is the count value of the carrier CR ′ in the carrier frequency adjustment section. The phase excess amount dθ is when the phase of the carrier CR ′ immediately after the phase θv of the voltage modulated waves Vu *, Vv *, Vw * becomes 0 (time a in the figure) becomes 0 (time b in the figure). Of the voltage modulation waves Vu *, Vv * and Vw *.

  In the carrier adjustment section S, the phase excess dθ is gradually absorbed in each carrier valley so that the phase of the carrier CR ′ also becomes 0 at the time when the phase θv of the voltage modulation wave becomes 0 next.

カウント値Ｘ'は、カウンタクロックをｆｍｍｔとし、式（４）に従い求められる。

Here, the count value Δcnt of the counter clock of the carrier generation unit 7 corresponding to the phase excess dθ is expressed by Expression (3) from dθ and the motor excitation frequency f1 when the counter clock is fmmt.

The count value X ′ is obtained according to equation (4), with the counter clock being fmmt.

  In order to gradually absorb the phase excess amount dθ for each mountain valley of the carrier, it is necessary to change the count value X ′ in the frequency adjustment section S to the count value Y ′, and the change amount ΔX ′ with respect to the count value X ′ at this time Is determined as follows.

  When the number of carrier peaks and valleys in the carrier frequency adjustment section S is 1 to k, the phase of the carrier CR ′ immediately after the phase θv of the voltage modulation waves Vu *, Vv *, and Vw * becomes 0 (time a) is 0. When the point at (time b) is the valley of the carrier, the number of carrier peaks and valleys in the section S is k times from 1 to k, so the change amount ΔX ′ is the count value Δcnt of the phase excess dθ. Can be divided by the number of times of carrier ridges and valleys k, which is calculated by equation (5).

なお、電圧変調波の位相θｖが０となった直後のキャリアＣＲ'の位相が０となる点がキャリア山の場合には、区間Ｓでのキャリア山谷の回数は（ｋ−１）回であり、ΔＸ'は式（６）に従い求められる。

When the point where the phase of the carrier CR ′ immediately after the phase θv of the voltage modulation wave becomes 0 is a carrier mountain, the number of carrier peaks and valleys in the section S is (k−1) times. , ΔX ′ is obtained according to the equation (6).

よって、図７のキャリア周波数調整区間ＳでのキャリアＣＲ'のカウント値Ｙ'は、式（７）に示すように、非同期ＰＷＭモードでのカウント値Ｘ'から変更量ΔＸ'を減算し算出する。

Accordingly, the count value Y ′ of the carrier CR ′ in the carrier frequency adjustment section S of FIG. 7 is calculated by subtracting the change amount ΔX ′ from the count value X ′ in the asynchronous PWM mode, as shown in Expression (7). .

式（７）で求めたカウント値Ｙ'をキャリアの谷１でセットし、キャリア山谷１からｋでキャリアと変調波の同期調整が実施され、キャリア及び電圧変調波の位相が０で同期が取れた時刻ｃで同期ＰＷＭモードでのカウント値Ｘ'に切り替える。

The count value Y ′ obtained by the equation (7) is set at the carrier valley 1, and the carrier and modulation wave are adjusted in synchronization from the carrier valley 1 to k, and the carrier and the voltage modulation wave are in phase 0 and synchronized. At time c, the count value is switched to the count value X ′ in the synchronous PWM mode.

  As described above, the pulsation of the motor torque at the time of switching from the asynchronous PWM mode to the synchronous PWM mode can be suppressed by the carrier adjusting operation by the carrier generating unit 7, and the switching can be suitably performed.

  A flowchart of the changing operation of the carrier frequency command fc * performed by the carrier frequency command unit 51 described above will be described with reference to FIG. In FIG. 8, in step 60, the carrier mode instruction unit 50 determines whether the motor 2 is accelerating / decelerating or settling based on the output from the speed detection sensor. In the case of acceleration / deceleration operation, the process proceeds to step 61.

  In step 61, when the motor 2 is accelerated or decelerated, the carrier mode instruction unit 51 sets an upper limit fc2 for the carrier frequency fc. Proceeding to step 62, the carrier mode instruction unit 51 determines whether or not the motor excitation frequency f1 is equal to or less than a predetermined value f1a. If the motor excitation frequency f1 is equal to or lower than the frequency f1a, the process proceeds to step 63, and if it exceeds the frequency f1a, the process proceeds to step 64.

  In step 63, since the motor 2 is driven in the asynchronous PWM mode, the asynchronous mode carrier frequency command unit 51a sets the carrier frequency command fc * to a constant value fc1 * and outputs the carrier frequency command in the asynchronous PWM mode to the carrier generation unit 7. fc * is output.

  Since the motor 2 is driven in the synchronous PWM mode when the motor excitation frequency f1 exceeds the frequency f1a, the synchronous mode carrier frequency command unit 51b sets the carrier frequency fc to a multiple of 3 with respect to the motor excitation frequency f1, and The carrier frequency command fc * limited to the frequency fc2 or lower is output to the carrier generation unit 7 (step 64).

  If it is determined in step 60 that determines the motor operation state that the motor 2 is performing a settling operation, the process proceeds to step 65. Asynchronous mode carrier frequency command unit 51a detects phase current I of motor 2 from motor current detector 10, and determines carrier frequency command fc * 'according to current I (step 65). When the carrier mode instructing unit 50 instructs the carrier generation in the synchronous PWM mode, the synchronous mode carrier frequency command unit 51b uses the carrier frequency command fc * ′ output in step 65 as the carrier frequency command fc in the synchronous PWM mode. The carrier frequency fc is adjusted so as to be * (step 66).

  Here, the determination of the carrier frequency command fc * ′ in step 65 will be described with reference to FIG. Since the switching loss of the switching element of the inverter 4 increases and decreases in proportion to the motor current and the switching frequency, the value obtained by multiplying the maximum motor current during acceleration and the carrier frequency at that time is used as a reference value for loss, and this reference value is used as the motor current. The carrier frequency command fc * ′ is obtained by dividing by the current I from the detector 10.

  At this time, since the carrier frequency command fc * ′ is expressed by an inversely proportional function of the current I, as shown in FIG. 9, when the current I is small, a restriction is applied so that the carrier frequency command fc * ′ is not increased to fc3 or more. ing. Further, since the motor current I at the time of settling is smaller than the motor current at the time of acceleration and no current greater than the motor current Ifc2 at the carrier frequency fc2 flows, the carrier frequency at the settling time is higher than the carrier frequency at the time of acceleration / deceleration. Is also kept high.

  If the number of carriers in one cycle of the motor excitation frequency f1 with respect to the carrier frequency command obtained in step 65 is, for example, less than 15 and cannot be sufficiently large, the three-phase phase current of the motor 2 may be unbalanced. In step 66, the carrier frequency command fc * ′ is adjusted to be lowered so that the PWM generation mode becomes the synchronous PWM mode.

  As described above, in the control device 100 according to the present embodiment, when the current of the motor 2 is reduced, the carrier frequency fc is increased to the maximum allowable heat generation amount of the switching element according to the magnitude of the motor current. The number of carriers in one period of the frequency can be increased. Therefore, it is possible to reduce the harmonic component of the motor current when the motor 2 is set, and to suppress the temperature increase of the ball bearing of the motor 2 bearing portion.

  When the number of carriers in one cycle of the motor excitation frequency when the motor 2 is set cannot be increased sufficiently, the carrier frequency fc is adjusted so as to be in the synchronous PWM mode. Therefore, it is possible to suppress the temperature increase of the ball bearing of the motor 2-bearing portion while preventing motor torque irregularity due to motor current imbalance.

  As described above in detail, according to the centrifuge provided with the control device 100 according to the present embodiment, the rotor 1 that stores the sample, the motor 2 that rotationally drives the rotor 1, and the current rotation of the motor 2 A speed detection sensor 3 that detects the speed, an inverter 4 that drives the motor 2, a control unit 5 that controls the inverter 4, and a motor current detector 10 that detects the current of the motor 2 are provided. A voltage modulation wave generation unit 6 that generates voltage modulation waves Vu *, Vv *, and Vw * that are targets of the phase voltage applied to the motor 2, a carrier generation unit 7 that generates a carrier CR, and a voltage modulation wave Vu *, A PWM signal generator 8 that outputs a PWM signal to the inverter 4 by comparing the magnitudes of Vv *, Vw * and carrier CR, and a carrier frequency that determines the carrier frequency and outputs a carrier frequency command to the carrier generator 7 The number indicating unit 9 is provided, and the carrier frequency indicating unit 9 makes the carrier frequency at the time of setting higher than the carrier frequency fc at the time of acceleration / deceleration during the acceleration / deceleration or settling operation of the motor at a predetermined motor excitation frequency. The harmonic component of the current can be reduced, the heat generation of the motor 2 can be suppressed even during driving in the PWM mode during settling, and the temperature rise of the ball bearing of the bearing portion of the motor 2 can be suppressed.

  The preferred embodiment of the motor control apparatus according to the present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiment. Those skilled in the art can make various modifications and improvements within the scope of the technical idea described in the claims.

  The control device according to the present invention can be used as a control device that drives and controls a motor for a centrifuge.

2 is a schematic cross-sectional view of a centrifuge 200 including a control device 100. FIG. 2 is a block diagram illustrating a configuration of a centrifuge 200 including a control device 100. FIG. It is a figure which shows the PWM signal generation method used as the switching signal of the inverter. 4 is a block diagram showing a detailed configuration of a carrier frequency instruction unit 9. FIG. It is a figure which shows the relationship between motor excitation frequency f1 and carrier frequency fc. It is a figure which shows the detail of change operation | movement of the carrier frequency fc. It is a figure which shows switching operation | movement from asynchronous PWM mode to synchronous PWM mode. It is a flowchart which shows the change operation | movement of carrier frequency fc. It is a figure which shows the relationship between the phase current I which flows through the motor 2 at the time of settling, and the carrier frequency fc.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Motor, 3 ... Speed detection sensor, 4 ... Inverter, 5 ... Inverter control part, 6 ... Voltage modulation wave generation part, 7 ... Carrier generation , 8 ... PWM signal generator, 9 ... carrier frequency indicator, 10 ... motor current detector, 100 ... control device, 200 ... centrifuge

Claims (4)

A speed detection sensor for detecting the rotational speed of the motor;
A drive unit for driving the motor;
A control unit for controlling the driving unit;
The control unit includes:
A voltage modulation wave generation unit that generates a voltage modulation wave that is a target of a phase voltage applied to the motor;
A carrier generator for generating carriers;
A drive signal generation unit that outputs a drive signal generated by a magnitude comparison between the voltage-modulated wave and the carrier to the drive unit;
A carrier frequency instruction unit that determines a carrier frequency of the carrier according to an operating state of the motor detected by the speed detection sensor, and outputs the carrier frequency to the carrier generation unit;
With
The motor control apparatus according to claim 1, wherein the carrier frequency instruction unit sets a carrier frequency at the time of settling of the motor to be higher than a carrier frequency at the time of acceleration / deceleration. The controller is
Asynchronous mode in which the carrier frequency is constant regardless of the change in the frequency of the voltage modulation wave, and the carrier frequency is an integer multiple of the frequency of the voltage modulation wave with the change in the frequency of the voltage modulation wave. Mode switching means for switching between a synchronous mode that always synchronizes the phase of the voltage modulation wave and the carrier,
Further comprising
The mode switching means is
At the time of acceleration / deceleration of the motor, when the frequency of the voltage modulation wave is a predetermined value or less, switch to the asynchronous mode, and when the frequency of the voltage modulation wave exceeds a predetermined value, switch to the synchronization mode,
2. The motor control device according to claim 1, wherein the motor is switched to a synchronous mode when the motor is set.   The control device further includes a motor current detector that detects a current of the motor, and the control unit determines the carrier frequency according to the magnitude of the current of the motor by the motor current detector during the settling operation of the motor. The control device according to claim 1, wherein the control device is adjusted. A motor,
A rotor connected to the motor and rotating;
The motor control device according to claim 1, which controls rotation of the motor;
A centrifuge characterized by comprising:

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